Variable resistance



Nova 1949 B. J. EDWARDS ET AL 2,486,931

VARIABLE RES I STANCE Filed Aug. 7, 1947 Inventor .EJ Js a 0' Ba g onaI: aaclis n (gm/y, b 0 Attorney Patented Nov. 1, 1949 VARIABLERESISTANCE Baden J olm Edwards and Donald Jackson, Cambridge, England,assignors bridge, England to Pye Limited, Cam- Application August 7,1947, Serial No. 767,116 In Great Britain April 19, 1939 Section 1,Public Law .690, August 8, 1946 Patent expires April 19,, 1959 Claims.(01. 201-42.)

The present invention relates to resistors of the wire wound orcomposite type, and has for its object to provide a device for obtaining'a variable tapping point which will maintain its adjustment while beingcheap and simple to manufacture and compact in construction.

The present invention consists in a variable electric resistor orpotentiometer of the wire wound or composite type having a contactslider engaging with the resistance element, wherein said slider ismovable over a slot in a member adjacent to the resistance element andis provided with means which project through the slot, and are operableto bind the slider to the member in an adjusted position andsimultaneously to deform the slider for the purpose of pressing it morefirmly into contact with the resistance element.

The slide may be a U-shaped member of resilient material having contactson opposed faces of the projecting limbs which are adapted to make asliding contact with a resistance element disposed between these limbs.The bridge piece joining the two limbs, is provided with a projectionconstituting a handle for easily adjusting the position of the slide onthe resistance element. The resistors may be mounted behind a panel withthe handle projecting through a slot therein, means being provided forlocking the handle to the panel. Such locking may be effected by meansof a nut in threaded engagement with the projection and disposed on theside of the panel opposite to that on which the U-shaped member isdisposed, so that on tightening the nut, the panel is gripped betweenthe nut and the bridge piece. As the member is of resilient material,and as the projection is disposed intermediate the two ends of thebridge piece, the efiect of tightening the nut may also be employed tobow the said part and thereby force the ends of the two limbs towardseach other thereby causing the contacts to press more firmly against theresistance element.

Therefore the contacts of the slide are more firmly pressed into contactwith the resistance element when the slide is locked, but loosened whenadjustment is to be made.

An embodiment will be described with reference to the accompanyingdrawings in which Fig. l is a view in perspective of a variable resistorincorporating the present invention and also shows the slider mechanismwith the resistance element removed.

Fig. 2 is an enlarged sectional view of Fig. 1.

In the construction illustrated, a cylindrical resistance element l ismounted on a panel 2 by means of upstanding lugs 3 riveted to the panelso as to be slightly spaced from the panel. A U-shaped member 4 ofresilient stamped metal, is provided from which small projections 5 arepressed out on opposed faces at or adjacent the ends of the limbs, toform contact members engaging the resistance element. A metal screw 5formed integral with the spacing member ill is secured by the rivetportion H on the member ID to the bridge portion of member I. Thespacing member, which has parallel sides and is slightly thinner thanthe thickness of the panel 2, is arranged in a slot 1 in the panel 2 andin sliding engagement with the walls thereof, the screw 6 projectingfrom the side of the panel rte-- mote from the resistance element 1. Aninsulating finger nut 8 larger than the width of the slot, is inthreaded engagement with the screw 6. A small strip 9 of resilientinsulating material is disposed between the member 10 and the bridgeportion of the member 4 and is adapted to engage with the surface of thepanel 2 for ensuring that the nut when tightened does not pull themember through the slot. To adjust the resistor, the nut 8 is loosenedand the slide moved to a desired position, where it is locked inposition by tightening the nut, whereupon, the contacts 5 close to gripthe resistance element 1 between them in the manner previouslyindicated. The right hand portion of Figure 2 shows the position whichthe U-shaped member 4 would assume, when the nut is tightened, if theresistance element l were not in position. In this manner a firm contactcan be ensured between the contacts and element when locked, whilst whenloosened the slide may be easily moved.

Due to the compact construction of the resistors, several may besimilarly positioned in close proximity thus obtaining a compactadjustable resistor panel. The resistor may be used as a variableresistance or, by making an electrical" connection with the slidingcontacts, as a potentiometer.

It will be understood that various modifications may be made withoutdeparting from the spirit of the invention. For example the lockingmeans may be a cam and lever device, whilst the U- shaped member may beformed partly of conducting and partly of insulating material. Thismember may also be formed of several parts instead of one as described.

Furthermore, if desired only the bridge piece joining the two limbs needbe of readily resilient material whilst the limbs may be of more rigidconstruction.

We claim:

1. A variable electric resistor comprising a resistance element.oielongated form, a member having a slot therein, means for supportingsaid resistance element so that it extends opposite to and in alignmentwith said slot, a U-shaped contact having its limbs embracing theresistance element and having a resilient bridge piece extending acrosssaid slot, a member connected to the bridge piece and passing throughsaid slot and provided with means at the side of the slot remote fromthe bridge piece for urging the bridge piece into a flexed positionacross the slot.

2. A variable electric resistor comprising a resistance element ofelongated form, a member having a slot therein, means for supportingsaid resistance element so that it extends opposite to and in alignmentwith said slot, a U-shaped contact having its limbs embracing theresistance element and having a resilient bridge piece extending acrosssaid slot, a screw member projecting from the bridge piece and slidablewithin the slot, and means for tightening the screw member for lockingthe contact in an adjusted position and drawing the bridge piece towardsthe slot to deform the bridge piece and urge the limbs of the contactinto firm engagement with the resistance element.

3. A variable electric resistor comprising a resistance element ofelongated form, a member having a slot therein, means for supportingsaid resistance element so that it extends opposite to and in alignmentwith said slot, a U-shaped contact having its limbs embracing theresistance element and having a resilient bridge piece extending acrosssaid slot, a guide block disposed and movable within said slot andsecured to the bridge piece, said guide block being thinner than thematerial in which .the slot is formed, a screw block reon saidprojecting from the side of said guide mote from the bridge piece, and anut screw whereby, upon tightening of the nut, the contact is locked inan adjusted position and the bridge piece is flexed towards the slot tourge the limbs of the contact into firm engagement with the resistanceelement.

4. A variable electric resistor comprising a resistance-element ofelongated form, a member having a slot therein, means for supportingsaid resistance element so that it extends opposite to and in alignmentwith said slot, a U-shaped contact having its limbs embracing theresistance element and having a resilient bridge piece extending acrosssaid slot, a strip of resilient material positioned between the bridgepiece and the slotted member and spanning the slot, a member projectingfrom said bridge piece and through the slot, and means for urging thebridge piece towards the slot to lock the contact in an adjustedposition and to deform the bridge piece and the strip and thereby urgethe limbs of the contact into firm engagement with the resistanceelement.

5. A variable electric resistor comprising a resistance element ofelongated form, a member having a slot therein, means for supportingsaid resistance element so that it extends opposite to and in alignmentwith said slot, a U-shaped contact having its limbs embracing theresistance element and having a resilient bridge piece extending acrosssaid slot, a guide block disposed and movable within said slot andsecured to the bridge piece, said guide block being thinner than thematerial in which the slot is formed, a strip of resilient materialpositioned between the bridge piece and the guide block and spanning theslot, a screw projecting from the side of said guide block remote fromthebridge piece, and a nut on said screw, whereby, upon tightening ofthe nut, the contact is locked in an adjusted position and the guideblock is drawn through the slot to deform the bridge piece and the stripand thereby urge the limbs of the contact into firm engagement with theresistance element.

BADEN JOHN EDWARDS. DONALD JACKSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,321,873 Ziegler Nov. 18, 19192,091,371 McMaster Aug, 31, 1937 2,253,318 Barrow et a1. Aug. 19, 1941

